ToeplitzMatrix.php

<?php

namespace App;

/**
 * Toeplitz Matrix
 *
 * Given an m x n matrix, return true if the matrix is Toeplitz. Otherwise, return false.
 * A matrix is Toeplitz if every diagonal from top-left to bottom-right has the same elements.
 * Example 1:
 * Input: matrix = [[1,2,3,4],[5,1,2,3],[9,5,1,2]]
 * Output: true
 * Explanation: In the above grid, the diagonals are: "[9]", "[5, 5]", "[1, 1, 1]", "[2, 2, 2]", "[3, 3]", "[4]".
 * In each diagonal all elements are the same, so the answer is True.
 *
 * https://leetcode.com/problems/toeplitz-matrix
 */
class ToeplitzMatrix
{
    /**
     * @param array<array-key, array<array-key, int>> $matrix
     * @return bool
     */
    public function isToeplitzMatrix(array $matrix): bool
    {
        for ($row = 0, $rowMax = count($matrix) - 1; $row < $rowMax; $row++) {
            for ($col = 0, $colMax = count($matrix[$row]) - 1; $col < $colMax; $col++) {
                if ($matrix[$row][$col] !== $matrix[$row + 1][$col + 1]) {
                    return false;
                }
            }
        }
        return true;
    }
}